电化学阻抗谱研究负向电压对AZ31B镁合金微弧氧化陶瓷层致密性的影响

采用单极性和双极性脉冲，分别改变几种不同正向电压时的负向电压，在AZ31B镁合金表面制备了微弧氧化膜。利用电化学阻抗谱和扫描电镜研究氧化膜的等效电路元件值以及微观结构的变化，从而分析负向电压对镁合金微弧氧化膜致密性的影响。结果表明：负向电压对于微弧氧化陶瓷膜致密性具有至关重要的作用，适当的负向电压可以有效地提高膜层致密性。并且，不同的正向电压下形成致密氧化膜的负向电压都约为30 V，不随正向电压变化而变化。

EFFECT OF NEGATIVE POTENTIAL ON COMPACTNESS OF PLASMA ELECTROLYTIC OXIDATION COATINGS ON MAGNESIUM ALLOY AZ31B BY ELECTROCHEMICAL IMPEDANCE SPECTRUM

The effect of negative potential of bipolar pulse on the compactness of plasma electrolytic oxidation (PEO) coating on magnesium alloy is not definite nowadays. PEO coatings on magnesium alloy AZ31B were prepared by respectively using unipolar and bipolar pulse whose negative potential was changed while positive potential was at several levels. In order to analyze the effect of negative potential on compactness of PEO coatings, the samples were examined by electrochemical impedance spectrum (EIS) and scanning electron microscope (SEM) to study the variation of equivalent circuit data and the change of macrostructure. The results have shown that negative potential plays an important role on compactness of PEO coatings and suitable negative potential can increase the compactness of coatings. The negative potential of pulse which can prepare compact coatings is always 30 V and stays the same at several levels of positive potential.